The invention relates to a method for operation of a motor vehicle having at least two drives. It also relates to a motor vehicle.
A method for operation of a motor vehicle having two electrical drives for different axles of the motor vehicle is known, in particular, from US 2009/0118924 A1. The method makes use of a control unit. This receives inputs, for example an input by which a specific torque is demanded, for example that resulting from the position of an accelerator pedal or gas pedal (this also applies to a brake pedal). Further inputs originate from a rotation speed sensor as well as sensors which relate to parameters such as pressure and temperatures of components of the motor vehicle, in particular of the motor or engine, and of the surrounding area as well. The controller then sends control signals to actuators which operate the motors or engines, for example fuel injectors, a throttle valve etc. A minimum and a maximum torque are determined for each motor or engine. Specific criteria are applied, with a distinction being drawn between three different cases here. Finally, an output torque is allocated to the individual motors or engines.
A demanded torque is also determined during operation of a motor vehicle having two motors or engines, according to DE 10 2006 000 306 A1. The calculation of the torque demand in this case includes the gear selection position, the vehicle speed, the rotation speeds of the two motors or engines as well as an input limit and an output limit of the battery. A lower torque limit is calculated for one motor or engine. This then results in a torque command to the relevant motor or engine, matched to the torque demand. The method from DE 10 2006 000 306 A1 is limited to a brake controller, that is to say it is used during braking of the motor vehicle.
DE 10 2004 034 401 A1 discloses a drive controller being used to match two drive units to one another such that a total drive power which is emitted by the two drive units in order to drive wheels corresponds to a driver demand output.
DE 10 2004 049 324 A2 describes that, in the case of a hybrid vehicle, the driver demand is determined by a first module as a function of a pedal position, and a value for a drive torque which corresponds to this driver demand is passed to a control unit where further measured values, such as the speed of travel etc., are taken into account, in order to calculate a distribution level which corresponds to the ratio of the torque from the electric motor to the drive torque. This distribution level is passed to a closed-loop control stage, which calculates a second distribution level, corresponding to driving dynamic functions. Both distribution levels are passed to a coordination stage, which uses actuation limits of the motor and engine to determine the final distribution level.
WO 2010/031678 A1 discloses that an overall drive torque is first of all determined in order to adjust a motor drive device having two drive units, and the torque distribution for the drive units is subsequently defined therefrom, taking account of constraints from driving-dynamic control systems. A consumption-optimum torque distribution is then calculated therefrom, taking account inter alia, of restrictions of originating from the motor or engine drive units. If this cannot be done, feedback is provided, as a result of which the consumption-optimum torque distribution is recalculated.
The methods which are known from the related art for operation of a motor vehicle having two drives ensure allocation of the demanded torque to the individual drives on the basis of specific criteria, such as the energy efficiency and/or the availability of current through a battery for one electrical drive. The distribution of torque to individual axles of the motor vehicle also, however, has a direct effect on the driving behavior of the motor vehicle. It is known for the torque to be moved from one axle to another axle in order to stabilize a motor vehicle, and possibly also from one wheel on one axle to another wheel on one axle.
It will be desirable to also ensure stabilization of the vehicle in a similar manner in a motor vehicle having two drives, at least in specific situations, where this is necessary, for example when turning or to improve the traction.